/*-----------------------------------------
   SKETCH.C -- Shadow Bitmap Demonstration
               (c) Charles Petzold, 1998
  -----------------------------------------*/

#include <windows.h>

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
	PSTR szCmdLine, int iCmdShow)
{
	static TCHAR szAppName [] = TEXT ("Sketch") ;
	HWND         hwnd ;
	MSG          msg ;
	WNDCLASS     wndclass ;

	wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
	wndclass.lpfnWndProc   = WndProc ;
	wndclass.cbClsExtra    = 0 ;
	wndclass.cbWndExtra    = 0 ;
	wndclass.hInstance     = hInstance ;
	wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;
	wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
	wndclass.hbrBackground = NULL; // (HBRUSH) GetStockObject (WHITE_BRUSH) ;
	wndclass.lpszMenuName  = NULL ;
	wndclass.lpszClassName = szAppName ;

	if (!RegisterClass (&wndclass))
	{
		MessageBox (NULL, TEXT ("This program requires Windows NT!"),
			szAppName, MB_ICONERROR) ;
		return 0 ;
	}

	hwnd = CreateWindow (szAppName, TEXT ("Sketch"), 
		WS_OVERLAPPEDWINDOW, 
		CW_USEDEFAULT, CW_USEDEFAULT,
		CW_USEDEFAULT, CW_USEDEFAULT,
		NULL, NULL, hInstance, NULL) ;

	if (hwnd == NULL)
	{
		MessageBox (NULL, TEXT ("Not enough memory to create bitmap!"),
			szAppName, MB_ICONERROR) ;
		return 0 ;
	}

	ShowWindow (hwnd, iCmdShow) ;
	UpdateWindow (hwnd) ;

	while (GetMessage (&msg, NULL, 0, 0))
	{
		TranslateMessage (&msg) ;
		DispatchMessage (&msg) ;
	}
	return msg.wParam ;
}

void GetLargestDisplayMode (int * pcxBitmap, int * pcyBitmap)
{
	DEVMODE devmode ;
	int     iModeNum = 0 ;

	* pcxBitmap = * pcyBitmap = 0 ;

	ZeroMemory (&devmode, sizeof (DEVMODE)) ;
	devmode.dmSize = sizeof (DEVMODE) ;

	while (EnumDisplaySettings (NULL, iModeNum++, &devmode))
	{
		* pcxBitmap = max (* pcxBitmap, (int) devmode.dmPelsWidth) ;
		* pcyBitmap = max (* pcyBitmap, (int) devmode.dmPelsHeight) ;
	}
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	static BOOL    fLeftButtonDown, fRightButtonDown ;
	static HBITMAP hBitmap ;
	static HDC     hdcMem ;
	static int     cxBitmap, cyBitmap, cxClient, cyClient, xMouse, yMouse ;
	HDC            hdc ;
	PAINTSTRUCT    ps ;

	switch (message)
	{
	case WM_CREATE:
		GetLargestDisplayMode (&cxBitmap, &cyBitmap) ;

		hdc = GetDC (hwnd) ;
		hBitmap = CreateCompatibleBitmap (hdc, cxBitmap, cyBitmap) ;
		hdcMem  = CreateCompatibleDC (hdc) ;
		ReleaseDC (hwnd, hdc) ;

		if (!hBitmap)       // no memory for bitmap
		{
			DeleteDC (hdcMem) ;
			return -1 ;
		}

		SelectObject (hdcMem, hBitmap) ;

		// Chj memo: Make the whole canvas WHITE. Would be whole black otherwise.
		PatBlt (hdcMem, 0, 0, cxBitmap, cyBitmap, WHITENESS) ;
		return 0 ;

	case WM_SIZE:
		cxClient = LOWORD (lParam) ;
		cyClient = HIWORD (lParam) ;
		return 0 ;

	case WM_LBUTTONDOWN:
		if (!fRightButtonDown)
			SetCapture (hwnd) ;

		xMouse = LOWORD (lParam) ;
		yMouse = HIWORD (lParam) ;
		fLeftButtonDown = TRUE ;
		return 0 ;

	case WM_LBUTTONUP:
		if (fLeftButtonDown)
			SetCapture (NULL) ;

		fLeftButtonDown = FALSE ;
		return 0 ;

	case WM_RBUTTONDOWN:
		if (!fLeftButtonDown)
			SetCapture (hwnd) ;

		xMouse = LOWORD (lParam) ;
		yMouse = HIWORD (lParam) ;
		fRightButtonDown = TRUE ;
		return 0 ;

	case WM_RBUTTONUP:
		if (fRightButtonDown) 
			SetCapture (NULL) ;

		fRightButtonDown = FALSE ;
		return 0 ;

	case WM_MOUSEMOVE:
		if (!fLeftButtonDown && !fRightButtonDown)
			return 0 ;

		hdc = GetDC (hwnd) ;

		SelectObject (hdc, 
			GetStockObject (fLeftButtonDown ? BLACK_PEN : WHITE_PEN)) ;

		SelectObject (hdcMem,
			GetStockObject (fLeftButtonDown ? BLACK_PEN : WHITE_PEN)) ;

		MoveToEx (hdc,    xMouse, yMouse, NULL) ;
		MoveToEx (hdcMem, xMouse, yMouse, NULL) ;

		xMouse = (short) LOWORD (lParam) ;
		yMouse = (short) HIWORD (lParam) ;

		LineTo (hdc,    xMouse, yMouse) ;
		LineTo (hdcMem, xMouse, yMouse) ;

		ReleaseDC (hwnd, hdc) ;
		return 0 ;

	case WM_PAINT:
		hdc = BeginPaint (hwnd, &ps) ;

		// Chj memo: One-time blit, thus eliminate screen flickering.
		BitBlt (hdc, 0, 0, cxClient, cyClient, hdcMem, 0, 0, SRCCOPY) ;

		EndPaint (hwnd, &ps) ;
		return 0 ;

	case WM_DESTROY:
		DeleteDC (hdcMem) ;
		DeleteObject (hBitmap) ;
		PostQuitMessage (0) ;
		return 0 ;
	}
	return DefWindowProc (hwnd, message, wParam, lParam) ;
}
